Participants in this open-label study will be recruited from two publicly funded community mental health agencies in Baltimore, MD. Participants will be randomly assigned to receive either enhanced treatment as usual or the STIRR intervention. Individuals assigned to STIRR will attend three sessions over the course of 6 months. The first session will involve education, personalized risk assessment, risk reduction counseling, pre-test counseling, blood testing, and an initial immunization with Twinrix for hepatitis A and B viruses (HAV and HBV). At the second session, participants will receive their test results, as well as post-test and risk reduction counseling, medical referral and linkage, if necessary, and a second Twinrix immunization. The third session will include an assessment of risk level and reinforcement of risk reduction, a final immunization, an assessment of progress on treatment and linkage, and behavior reinforcement or modification. Enhanced treatment as usual will entail comprehensive mental health services provided at each study site, education about blood-borne diseases, and referral to a local community health provider for blood testing, HAV and HBV immunizations, and any necessary treatments. All participants will be assessed for treatment outcomes at Month 6. A 12-month post-intervention follow-up will be carried out with the infected participants in the STIRR group to evaluate quality of care.